Experimental study on the effect of undulating pipeline on sand transport in multiphase flow

Previous research work has shown that sand production with hydrocarbons has helped to increase the productivity of oil wells. However, this poses difficulties during shut down and start-up operations due to sand deposition and are aggravated when the pipelines are undulating. The hilly-terrain geometry of pipelines strongly affects multiphase flow regimes hence the need to study sand transport characteristics as it is vital in efficient pipeline design. The aim of this research work is to experimentally investigate the flow hydrodynamics that exist during sand transport in multiphase flow at different sand concentration. A 2-inch dip facility which consists of a downhill pipeline section, a lower elbow (dip) and an uphill pipeline at inclination angles of 24° is used in the study. Extensive data were collected and analysed from continuous measurement of instantaneous liquid and sand hold up using conductivity rings and flow visualisation using a high speed camera. Results show that five different flow patterns were obtained from the sand-water test both via visual observation and from the conductivity rings data namely: full suspension, streak, saltation, sand dunes and sand bed. The knowledge of flow at minimum transport condition and full suspension establishes the erosion rate over the life span of the pipeline. In contrast, the sand holdup measurement and sand dune regime which was uniquely identified using the conductivity ring method would help overcome the limitation of sand measurement in pipeline. Also, the Sand-Air-Water experiment carried out shows the influence of the pipe geometry and multiphase flow regimes on sand transport in multiphase transport pipelines.